In recent years, flat panel display devices that use flat panel display elements such as liquid crystal panels and plasma display panels are increasingly used as display elements for image display devices such as television receivers instead of conventional cathode-ray tube displays, allowing image display devices to be made thinner. Liquid crystal panels used in liquid crystal display devices do not emit light on their own, and therefore, it is necessary to provide a separate backlight device as an illumination device. A known example of such a backlight device is an edge light-type backlight device in which a light-receiving surface is provided on a side face of a light guide plate, and a light source such as an LED is provided facing the side face of the light guide plate.
Patent Document 1 discloses an edge light-type backlight device provided with a structure that sets the position of the light guide plate. In this backlight device, a light-receiving surface is provided on one side face of the light guide plate, and a light source substrate is provided only at the one side face of the light guide plate. Elastic spacers are provided respectively between the light source substrate and the light guide plate, on both sides of the light source substrate. In this backlight device, the gap between the light source substrate and the light guide plate is set by the elastic spacers, thereby setting the position of the light guide plate.